Me: BW, divorced, now fabulous and happy!
Timing for the divorce depends on the state as well as the individual facts of your case, like dmari said. Mine was final about 4 months after filing, as that's the mandatory waiting period in my state.
I know it sucks, but on the bright side, you are only 26 and haven't wasted a lifetime with a cheater. I know that there is a fabulous new life out there waiting for you and your son once you get through this process and heal. Some day in the future, you will realize how lucky you are to be free of him.
They always say that it's better to come from a broken home than live in a broken home, and I believe that to be true. Also, as long as the child has one good, stable parent (you) he'll be fine.
I'm sorry you had another D-Day (but don't beat yourself up; that seems to be more the norm than the exception) and I know you're hurting now, but it will get so much better. Promise.
Married: 11 years, no kids
Character is destiny